This invention relates to an improved device for the external fixation of bone fractures, in particular ankle fractures.
More specifically, the invention relates to a device adapted for mounting to an external fixator and comprising an extendible central body and opposed articulated portions which are connected to respective ends of the central body by ball joints.
The use of external fixators capable of setting bone fractures in highly delicate regions of the human skeleton, and especially in the proximity of joints, is common practice in the instant field.
As an example, for treating fractures of the tibial stem, and to prevent the inception of arthrodesy and arthrodiastasis of the ankle, unilateral external fixators are often used which have a main body and articulated portions joined to the central body by means of ball joints. The articulated portions are to be secured to the tibia and the ankle bones by means of rod-like fastening screws.
A prior external fixator for setting fractured ankles is described, for example, in the International Patent Application No. WO97/10775 to this same Applicant.
Also as an example, FIG. 1 of the accompanying drawings illustrates the use of a fixator sold by the Applicant. To more clearly show how this fixator is applied, the perspective view of FIG. 1 includes the bone parts affected by the operation, namely a tibia T and tibia-tarsus joint Ts.
The fixator shown in FIG. 1 comprises a central body 2 of substantially cylindrical shape that can be extended axially and has opposite ends attached to respective articulated portions 3 and 4.
A first portion 3, referred to as proximal hereinafter, is secured realisably to the tibia by means of rod-like screws 5, which are threaded into the shinbone. Two or three of such screws usually provide sufficient holding power.
The proximal portion 3 is connected to one end of the central body 2 through a ball joint 6 which has Allen screw fasteners associated therewith at that end of the central body 2.
A second articulated portion 4, referred to as distal portion, is secured realisably to the ankle bones by means of rod-like screws 9 which are threaded into the talus and the calcaneus, respectively. The distal portion 4 is connected to the other end of the central body 2 through a ball joint 6, also having Allen screw fasteners associated therewith.
The distal portion 4 is better known in the art as the xe2x80x9cankle clampxe2x80x9d, and will be indicated by this term hereinafter.
The ankle clamp 4 in FIG. 1 comprises a bifurcate stem 10 having a pair of prongs 11, 12 whose free ends mount a clamp member 15. The prongs 11, 12 are bored through across each free end. The through-going bores at the two ends are coaxial and accommodate an Allen-head bolt.
The clamp member 15 comprises a pair of jaws 16, 17 having mating inward contours which fit centrally around the bolt shank and clamp with their ends around the rod-like screws 9 to immobilise the calcaneus and tarsus. Coaxial holes are provided through the opposite ends of the jaws 16, 17 to receive respective bolts 18, 19 for tightening the jaws onto the rod-like screws 9.
While being advantageous in many ways and substantially serving its purpose, the above ankle clamp has some drawbacks, as follows.
Since the clamp member 15 with the jaws 16, 17 is fastened to the prongs 11,12 of the bifurcate stem 10 by means of an Allen-head bolt, is difficult for the surgeon to couple the components of the clamp. Moreover, two different clamp members must be used depending to the use on a right or a left limb respectively.
Moreover, the clamp stem partly conceals the joint, so that the surgeon is forbidden a clear view of the tibia-tarsus joint, even if radiographic.
This represents a serious shortcoming because a restricted view of the joint makes more difficult reducing the fracture, and also inspecting the healing bone periodically for later evaluation; most importantly, a restricted view of the joint makes very difficult the locating of the pivot centre of the tibia-tarsus joint, on which depends the proper positioning of the screws in the calcaneus and the talus for securing the clamp.
If the pivot centre as estimated by the surgeon does not correspond with the true pivot centre of the ankle, the joint may undergo diastasis and compression, and ligaments become strained.
To obviate, at least in part, these drawbacks, a solution has been proposed in the art and described in sales catalogues. This prior solution consists of providing the ankle clamp with a C-shaped stem effective to leave the surgical area view unobstructed.
However, this prior solution is unsatisfactory on account of the following:
The C-shaped stem is not coaxial with the other portions of the fixator, which potentially detracts from the overall structure rigidity;
A fixator having a C-shaped stem cannot be used for left-side and right-side broken limbs; thus, separate fixators must be made available for application to left and right limbs, since converting an fixator on the occasion of a surgical intervention would be an inconvenient and complicated procedure;
The C-shaped stem produces an offset bulk which can be of hindrance to the surgeon during the operation, as well as to the convalescing patient;
Finally, there still exists a blocked direction to X-raying.
The underlying technical problem of this invention is that of providing an improved ankle clamp which can be easily and directly used for both left- and right-side broken limbs.
Another aim of the present invention is that of contriving an improved ankle clamp having such construction and functional features to provide the surgeon with an unrestricted view of the joint being treated from all directions, while holding the fixator coaxial with the ankle clamp mounted to it.
The above technical problem is solved by a device as previously indicated and defined in the characterising portions of Claim 1 and following.
The features and advantages of an ankle clamp according to the invention will be apparent from the following description of an embodiment thereof, given by way of non-limiting example with reference to the accompanying drawings.